feat: introduce workflow management tools and commands

- Added new workflow commands: `/workflow` to open the workflow panel and `/workflow run <prompt>` to execute workflows.
- Implemented `spawn_agents` and `spawn_pipeline` tools for parallel and sequential task execution, respectively.
- Enhanced workflow engine to handle real-time agent status updates and display in the UI.
- Updated workflow panel to show agent statuses, findings count, and session counters.
- Refactored existing code to integrate new workflow functionalities and improve overall structure.

src/app/subagent/context.rs

@@ -18,12 +18,13 @@ pub struct SubagentContext {
 
 /// Build a `SubagentContext` from an `AgentDefinition`.
 ///
-/// Flow: copy optional `allowed_tools` from the def -> fall back to the
-/// reviewer-allowlist when the def has none and the role is "reviewer" ->
+/// Flow: copy optional `allowed_tools` from the def → fall back to the
+/// reviewer-allowlist when the def has none and the role is "reviewer" →
 /// fall back to an empty list (i.e. "all tools allowed") for other roles.
+/// `max_steps` is read from the definition, defaulting to 25 if absent.
 ///
 /// Return: a context with empty `system_prompt` and `session_dir`,
-/// `max_steps = 25`, and the resolved allowed-tool list.
+/// resolved `max_steps`, and the resolved allowed-tool list.
 pub fn build_subagent_context(def: AgentDefinition) -> SubagentContext {
     let allowed_tools = def.allowed_tools.clone().unwrap_or_else(|| {
         if def.role == "reviewer" {
@@ -32,10 +33,11 @@ pub fn build_subagent_context(def: AgentDefinition) -> SubagentContext {
             Vec::new()
         }
     });
+    let max_steps = def.max_steps.unwrap_or(25);
     SubagentContext {
         system_prompt: String::new(),
         allowed_tools,
-        max_steps: 25,
+        max_steps,
         session_dir: PathBuf::new(),
     }
 }